In the remote sensing/aerial imaging industry, imagery may be used to capture views of a geographic area in order to measure objects and/or structures within the images. These are generally referred to as “geo-referenced images” and come in two basic categories:
Vertical Imagery—images captured with a camera pointed vertically downward thus generally capturing the tops of structures; and
Oblique Imagery—images captured with a camera aimed at an angle capturing the sides, as well as, tops of structures.
Most vertical imagery may be processed in order to fit a mathematically rectangular projection or map. This process is known as ortho-rectification and attempts to create an appearance as if the sensor were directly above each pixel in the image. The resulting image is known as an ortho-photo. Since the images are mathematically projected, they may be combined into a seamless mosaic resulting in a composite image known as an ortho-mosaic. The term ‘ortho image’ is used to denote a geo-referenced image that is either an ortho-photo image or an ortho-mosaic image.
Because they are captured looking straight down, an ortho-photo or ortho-mosaic contains a view of the world to which many are not accustomed. As a result, there may be difficulty in distinguishing between two different properties (e.g., buildings, structures, and/or other man-made or natural objects or features) as the only portions of the structures visible in the ortho-mosaic are rooftops. An oblique image, in contrast, is captured at an angle showing sides of objects and structures. Aerial imagery may be used in identification of dimensions of buildings or structures. Traditional ortho-rectified imagery has limited use, however, because it reveals only the edge of the roof and does not reveal several important aspects of the building.